Custom PC. Q4400, 8GB Ram, Vista Business x64, nvidia Quadro (latest drivers)
I installed Boxee to a non-default drive letter (H:), perhaps that is an issue.
The app runs for 3-4 seconds, screen flickers a bit, then closes. No messages. Nothing in the event logs.
I was able to get it running this morning on my ancient M200 Toshiba laptop (x86).
Let me know if I can provide any additional diagnostics.